1. Field of the Invention
The present invention relates to an arithmetic unit and more particularly an arithmetic unit for an electronic computer which executes useful bit processing instructions.
2. Technical Background and Problems of the Invention
TEST instruction, SET instruction and RESET instruction have been known as bit processing instructions for processing the information at a specified bit in an accumulator. The TEST instruction is such that the information at a specified bit in an accumulator ACC is transferred into a flag register FR. The SET instruction and the RESET instruction are such that "1" and "0" are written into specified bits of the accumulator ACC. Examples of the TEST, SET and RESET instructions are shown in FIGS. 1(a), (b) and (c), respectively.
There is a need that the information at a certain bit (for example, J bit) in an accumulator is written into another bit (for example K bit). So far this operation has been carried out with the above described instructions as follows:
______________________________________ TEST J JUMP P IF J = 0 SET K JUMP P + 1 P RESET K P + 1 (next instruction) ______________________________________
As described above, so far five steps are needed in order to transfer the information at one bit to another bit so that the programming is rather complex and the processing time is relatively long.
The reason is that so far the technical improvements of electronic computers are mainly directed to arithmetic operations, but little attention is paid to the improvement of bit processing control.